Pallet positioning and fixing device

ABSTRACT

A pallet positioning and fixing device is provided which has a simple constitution and is capable of positioning a work piece holding pallet to a high degree of accuracy in the horizontal direction and vertical direction, with respect to a base body. In the pallet positioning and fixing device ( 1 ), a horizontal receiving face ( 14 ) is formed on the upper face of a base body ( 2 ), a ring-shaped abutting face ( 37 ) which abuts against the receiving face ( 14 ) is provided on the lower face of the pallet ( 3 ), a clamping mechanism ( 4 ) is provided in substantially the central portion of the base body ( 2 ) and the pallet ( 3 ), a first positioning mechanism ( 5 ) capable of positioning the pallet ( 3 ) in a horizontal direction and a second positioning mechanism ( 6 ) capable of positioning a pallet ( 3 ) so as to prevent the same from rotating about a vertical axis are provided on either side of the clamping mechanism ( 4 ), the pallet ( 3 ) is positioned in the vertical direction by the receiving face ( 14 ) and the abutting face ( 37 ), and is positioned in the horizontal direction by the positioning mechanism ( 5, 6 ), and the pallet ( 3 ) is fixed to the base body ( 2 ) by the clamping mechanism ( 4 ).

TECHNICAL FIELD

The present invention relates to a device for positioning and fixing awork piece holding pallet, on a base body provided on the side of atable of a machine tool, and more particularly, to a device havingreduced numbers of positioning mechanisms and clamping mechanisms andsimplified constitution.

BACKGROUND OF THE INVENTION

In a machine tool, such as a machining centre, or the like, a base bodyis installed on a table, or a base body as a table itself is installed,a pallet holding one or more work piece is conveyed to the base body tobe fixed thereon, and machining is carried out on the work piece in apositioned and fixed state on the base body.

Recently, maximum machining accuracy of approximately 1 μm has come tobe required in machining for precision machine components, and thereforethe accuracy of positioning and fixing of the pallet with respect to thebase body has become extremely important. More specifically, this isbecause machining accuracy deteriorates in accordance with the erroroccurring when the pallet is positioned on and fixed to the base body.

In the prior art, Japanese Patent Laid-open No. 2000-117572 discloses apositioning and fixing device of a type wherein a pallet for holding awork piece is rotated, and this rotational movement being indexed intorespective small angles. In the device disclosed in this patentpublication, a clamping mechanism for fixing a pallet to a palletsupporting body is provided, positioning pins for restricting the palletsuch that it does not rotate about a vertical axis with respect to thepallet supporting body are provided, and the pallet performs indexedrotation together with the pallet supporting body. The clampingmechanism is constructed for clamping the pallet by means of drivingdownwards a collet expandable in diameter, but there is no descriptionof any mechanism for positioning the pallet in its height position andhorizontal position, with a high degree of accuracy.

Furthermore, Japanese Patent Laid-open No. 8-25167 describes apositioning and fixing device wherein one set of clamping mechanism isprovided in a central portion of a base body on a table, and a pallet,and four sets of positioning mechanisms are provided around the clampingmechanism. In this device, each positioning mechanism comprises atapered shaft section on the base body side and a tapered bush on thepallet side, the pallet being positioned with respect to the base bodyby means of fitting the tapered bush externally of the tapered shaftsection.

Other pallet positioning and fixing devices have a constitution whereinfour sets of positioning and fixing mechanisms are provided, and thepallet can be positioned and fixed in the vertical direction and thehorizontal direction by one set of of the positioning and fixingmechanisms, the pallet can be positioned and fixed in the verticaldirection and a direction about the vertical axis passing through thecentre of the pallet, by a positioning mechanism located on the oppositeside from the aforementioned mechanism with respect to the centre of thepallet, and the pallet can be positioned and fixed in the verticaldirection by means of the remaining two sets of positioning mechanisms.

In this pallet positioning and fixing device, a tubular shaft section, ataper collet fitted externally over this tubular shaft section, a springmember which drives the tapered collet in an upward direction, and areceiving face, are provided on a base body on the table side, and byfitting a tapered bush provided on the pallet externally over thetapered collet in close contact manner, and causing the lower face ofthe tapered bush to abut against the receiving face, the pallet ispositioned in the vertical direction and the horizontal direction.

The device described in Japanese Patent Laid-open No. 2000-117572 is ofa type wherein the pallet is fixed by one of the clamping mechanisms,but this device involves an improvement of the clamping mechanism, andthe construction for positioning the pallet to a high degree of accuracyin the horizontal direction and the vertical direction with respect tothe pallet supporting body is not described clearly. The positioning pinaccording to this patent publication serves to determine the rotationalposition of the pallet about a vertical axis with respect to the palletsupporting body, but it is not used to position the pallet with a highdegree of accuracy in the horizontal direction.

Furthermore, the device disclosed in above Japanese Patent Laid-open No.8-25167 achieves positioning by fitting a tapered shaft sectionexternally over a tapered bush, in four sets of respective positioningmechanisms, but in order to position the pallet with a high degree ofaccuracy in the horizontal direction, extremely high machining accuracyis required in the tapered shaft section and the tapered bush. Moreover,there is no description of any kind regarding a construction forpositioning the pallet to a high degree of accuracy in the verticaldirection.

Furthermore, in a device having four sets of positioning and fixingmechanisms as described above, highly accurate positioning in thevertical direction and the horizontal direction is achieved bypositioning the pallet in the vertical direction by causing the lowerfaces of the tapered bushes to abut against the receiving faces of thetubular shaft sections, and by positioning the pallet in the horizontaldirection by interposing tapered collets between the tubular shaftsections and the tapered bushes. But since the pallet is positioned onand fixed to the base body by means of four sets of positioning andfixing mechanisms, then four sets of clamping mechanisms and positioningmechanisms, each having many components and a complicated structure, arerequired, and hence the structure of the pallet positioning and fixingdevice become complicated.

Moreover, since a tapered collet is provided on the base body side,effects due to the degree of close contact of the inner and outer facesof the tapered collets, and the abrasion and settling thereof, and thelike, appear in all of the pallets to be set on the base body, andundesirably, as a consequence, this influences the machining error ofthe work piece which is arranged on the pallet.

The object of the present invention is to provide a positioning andfixing device having a simple structure whereby a pallet can bepositioned with a high degree of accuracy in the horizontal directionand the vertical direction, with respect to a base body.

DISCLOSURE OF THE INVENTION

The pallet positioning and fixing device according to the presentinvention is a pallet positioning and fixing device for positioning awork piece holding pallet and fixing the same releasably on a base bodyprovided on the table or provided as the table itself of a machine tool.

This pallet positioning and fixing device is characterized in that; ahorizontal receiving face is formed on an upper face of the base body,and an abutting face capable of positioning the pallet in a horizontalattitude by abutting against the receiving face is provided on a lowerface of the pallet; one set of clamping mechanism capable of pulling thepallet towards the base body and fixing it thereto is providedsubstantially in the central portion of the base body and the pallet;and a first positioning mechanism for positioning the pallet in ahorizontal direction with respect to the base body is provided on oneside of the clamping mechanism, and a second positioning mechanism forpositioning the pallet with respect to the base body so as to preventthe pallet from rotating about a vertical axis is provided on the otherside of the clamping mechanism.

When positioning the pallet, the pallet is positioned in a horizontalattitude (in other words, it is positioned in the vertical direction) bymeans of the abutting face provided on the lower face of the palletbeing abutted against the horizontal receiving face on the upper face ofthe base body, the pallet is positioned in the horizontal direction withrespect to the base body by means of the first positioning mechanism,the pallet is positioned in such a manner that it does not rotate abouta vertical axis with respect to the base body by the second positioningmechanism, and the pallet is fixed to the base body by means of a singleset of clamping mechanism. The receiving face may be formed continuouslyon the upper face of the base body, or it may be constituted with aplurality of receiving faces formed at separate radial positions on theupper face of the base body.

According to this positioning and fixing device, it is possible toposition the pallet in the horizontal attitude by means of a simpleconstitution wherein an abutting face of the pallet abuts against thereceiving face of the base body. Moreover, since the pallet can bepositioned in the horizontal direction with respect to the base body bymeans of the first positioning mechanism, and since the pallet can bepositioned in such a manner that it does not rotate about a verticalaxis with respect to the base body by means of the second positioningmechanism, it is possible to position the pallet with a high degree ofaccuracy in the vertical direction and horizontal direction, withrespect to the base body.

In this way, since it is possible to provide a single set of clampingmechanism, and two positioning mechanisms, the number of clampingmechanisms and positioning mechanisms each being composed of manycomponents and having complicated structure can be reduced to a minimum,the constitution of the pallet positioning and fixing device can besimplified, and the manufacturing costs can be reduced remarkably.

The first positioning mechanism may comprise a full circumferencetapered shaft section fixed to the base body and a first tapered colletprovided on the pallet in such a manner that it can be fitted tightlyover the full circumference tapered shaft section from above. In thiscase, when positioning the pallet, the first tapered collet makes closecontact with the full circumference tapered shaft section at the fullface of the inner circumferential face thereof, whilst the diameterthereof changes, and the pallet is positioned with a high degree ofaccuracy in the horizontal direction with respect to the base body, bymeans of the first positioning mechanism. More particularly, since thefirst tapered collet is provided on the pallet, then even if wearing orsettling has occurred in the first tapered collet due to repeated use,the effects thereof are not received by the base body, and hence errordoes not occur in the positioning of the pallet, when another pallet ispositioned and fixed.

The second positioning mechanism may comprise a two-face tapered shaftsection fixed to the base body and a second tapered collet provided onthe pallet in such a manner that it can be fitted over the two-facetapered shaft section from above. In this case, the two-face taperedshaft section has two tapered faces bordering in the circumferentialdirection about a vertical axis passing through the centre of the basebody, and when positioning the pallet, the second tapered collet makesclose contact with the two tapered faces whilst the diameter thereofchanges, and the pallet is positioned by the second positioningmechanism in such a manner that it does not rotate about the verticalaxis with respect to the base body. More particularly, since the secondtapered collet is provided on the pallet, then even if wearing orsettling has occurred in the second tapered collet due to repeated useof the pallet, then the effects of this are not received by the basebody and no error in positioning occurs if another pallet is positionedand fixed.

If the receiving face is a ring shaped face of a predetermined width andis formed as a ring shaped face which substantially intersects with thefirst and second positioning mechanisms, then when positioning thepallet, the abutting face of the pallet abuts against this ring-shapedface, and the pallet is positioned in the horizontal attitude.

If elastic members for respectively urging the first and second taperedcollets elastically in a downward direction are provided, then since thefirst and second tapered collets are urged elastically in the downwarddirection, when positioning the pallet, the full circumference taperedshaft section makes close contact with the two face tapered shaftsection whilst the diameter thereof changes, and the pallet ispositioned with a high degree of accuracy in the horizontal directionwith respect to the base body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a pallet positioning andfixing device according to an embodiment of the present invention;

FIG. 2 is a plan view of a pallet;

FIG. 3 is a front view of the positioning and fixing device;

FIG. 4 is a plan view of a base body;

FIG. 5 is a sectional view along line A-A in FIG. 2 of the positioningand fixing device (in a state where fixing is released);

FIG. 6 is a sectional view along line B-B in FIG. 2 of the positioningand fixing device (in a state where fixing is released);

FIG. 7 is an perspective view of the first and second tapered collet;

FIG. 8 is a sectional view of the first and second tapered collet;

FIG. 9 is an equivalent diagram to FIG. 5 of the positioning and fixingdevice (in a fixed state);

FIG. 10 is an equivalent diagram to FIG. 6 of the positioning and fixingdevice (in a fixed state);

FIG. 11 is a vertically cross sectional view of a pallet positioning andfixing device according to a modification; and

FIG. 12 is an equivalent diagram to FIG. 4 of the modification.

PREFERRED EMBODIMENT OF THE INVENTION

Below, a preferred embodiment of the present invention is described. Asshown in FIG. 1 to FIG. 4, a pallet positioning and fixing device 1positions a work piece holding pallet 3 for holding a work piece to besupplied to machining, on a base body 2 which is provided on the tableor provided as the table itself of a machine tool, and fixes the palletin a releasable manner.

The positioning and fixing device 1 is provided with the base body 2, asingle set of clamping mechanism 4 which is capable of fixing the pallet3 by pulling the pallet 3 towards the base body side at substantiallythe central portion of the pallet 3, a first positioning mechanism 5 forpositioning the pallet 3 in the horizontal direction with respect to thebase body 2, and a second positioning mechanism 6 for positioning thepallet 3 in such a manner that it does not turn about a vertical axiswith respect to the base body 2.

As shown in FIG. 3 to FIG. 6, the base body 2 is constituted with a baseplate 10 of substantially square shape in plan view, which is fixed onthe table of the machine tool, and a reference body 11, which isdisposed in the central portion of the upper face of the base plate 10.Air passages 12 for supplying compressed air for removing dirt are alsoformed in the reference body 11. The reference body 11 comprises a lowerlarge diameter section 11 a, a cylindrical section 11 b extendingupwards from the large diameter section 11 a, and an engaging section 11c which projects from the lower end of the large diameter section 11 a.A cylinder hole 42 and a rod insertion hole 13 into which a piston rod43 b of the clamping mechanism 4 is inserted are formed inside thereference body 11.

The reference body 11 is fixed to the base plate 10 by a plurality ofblots passing through the large diameter section 11 a, in a state wherethe engaging section 11 c thereof has been engaged with a hole 10 a inthe base plate 10. A flat receiving face 14 for positioning the pallet 3in a horizontal attitude by receiving the pallet 3 and positioning it inthe vertical direction is formed on the upper face of the large diametersection 11 a. In order that the pallet 3 is caused to make close contactin a stable fashion with the receiving face 14, when the pallet 3 abutsagainst the receiving face 14, the receiving face 14 is a ring-shapedface having a predetermined width, being formed as a ring-shaped facewhich intersects substantially with first and second positioningmechanisms 5, 6.

Two accommodating holes 15, 16 for accommodating a first tapered pin 60of the first positioning mechanism 5 and a second tapered pin 66 of thesecond positioning mechanism 6 are provided in two symmetrical positionswith respect to a central axis C in the vicinity of the upper face ofthe large diameter section 11 a, and recessed holes 15 a, 16 a whichconnect to the lower end of the respective accommodating holes 15, 16are also formed therein.

Six connecting holes 17 which connect through from the rod insertionhole 13 to the outer circumferential face are formed in the cylindricalsection 11 b, and a ring-shaped retainer 19 holding a steel ball 18 isengaged with and fixed into each of the respective connecting holes 17.The cylindrical section 11 b, connecting holes 17, steel balls 18 andretainers 19 are included in the clamping mechanism 4 describedhereinafter.

A dust seal 20 for preventing infiltration of cutting chips and dust isprovided on inner circumferential surface of the upper end section ofthe cylindrical section 11 b. A seal member 21 for performing sealing isprovided on the outer circumferential portion of the engaging section 11c.

An air passage 12 is connected to the air passage 10 b in the base plate10, and the air passage 12 is connected to the rod insertion hole 13. Aplurality of blow holes 22 passing in diagonal upwards directions areformed in the cylindrical section 11 b. When the pallet 3 is fixed tothe base body 2, pressurized air supplied to the air passage 12 flowsinto the rod insertion hole 13 and is expelled from the plurality ofblow holes 22, thus removing dirt from the pallet 3 by means of airblowing.

As shown in FIG. 1, FIG. 5 and FIG. 6, the pallet 3 comprises a palletmain body 30 which is substantially square in shape and a bush 31 formedwith an abutting face 37 which abuts against the receiving face 14 ofthe base body 2. A cylindrical accommodating hole 30 a having an openlower end is formed in the lower portion of the pallet main body 30, anda recessed hole 30 b connecting to the central portion of the upper endof the accommodating hole 30 a is also formed. A circular disc shapedbush 31 having a circular hole formed in the central portion thereof isfitted inside the accommodating hole 30 a and fixed by a plurality ofbolts 32. A ring-shaped shim plate 33 for adjusting the height positionof the bush 31 is installed at the upper end of the accommodating hole30 a.

Two circular cylindrical accommodating holes 31 a, 31 b having openlower ends are formed in a symmetrical fashion about a central axis C inthe lower portion of the cylindrical bush 31, and a first tapered collet34 of the first positioning mechanism 5 and a second tapered collet 35of the second positioning mechanism 6 are respectively installed inthese two accommodating holes 31 a, 31 b. An engaging section 36 withwhich the steel balls 18 engage when clamping is provided on the innercircumferential section of the upper end section of the bush 31, andthis engaging section 36 projects towards the inner side beyond theinner circumferences of the recessed hole 30 b and the shim plate 33. Ahorizontal ring-shaped abutting face 37 which abuts against thereceiving face 14 of the large diameter section is provided on the lowerface of the bush 31.

As shown in FIG. 5, the clamping mechanism 4 is provided in the centralportion of the base body 2 and the pallet 3, and the clamping mechanism4 comprises a hydraulic cylinder 40 for generating a clamping force anda clamping release force, and an engaging mechanism 41 for pulling thepallet 3 toward the side of the base body 2.

The double-acting type hydraulic cylinder 40 is disposed inside thecentral portion of the reference body 11, and this hydraulic cylinder 40comprises a cylinder hole 42 formed in the reference body 11, a pistonmember 43 for transmitting clamping force and clamping release force, aclamping oil chamber 44 for generating clamping force, a clampingrelease oil chamber 45 for generating clamping release force, and aplurality of springs 46 which are capable of maintaining a clampingstate, even in the event of a leak of hydraulic pressure.

The piston member 43 comprises an integrally formed piston 43 a andpiston rod 43 b, the piston 43 a being installed slidably up and down ina cylinder hole 42 and a seal member 47 being provided on the piston 43a, and the piston rod 43 b is able to slide up and down in the rodinsertion hole 13, a sealing member 48 for sealing the clamping oilchamber 44 also being provided. A ring-shaped engaging section 49 isprovided in the vicinity of the upper end of the piston rod 43 b, and aring-shaped recess section 50 is provided on the lower portion of thering-shaped engaging section 49.

The clamping oil chamber 44 is provided on the upper side of the piston43 a and the clamping release oil chamber 45 is provided on the lowerside of the piston 43 a. A ring member 51 for restricting the lowerlimit position of the piston 43 a is installed on the lower end portionof the cylinder hole 42, and the ring member 51 is held in position by alocking ring 52. Hydraulic pressure can be supplied to the oil chamber44 from an oil passage 44 a, and hydraulic pressure can be supplied tothe oil chamber 45 from an oil passage 45 a. A plurality of springaccommodating holes 53 which connect to the upper end of the cylinderhole 42 are formed, and each spring 46 is disposed in each of the springaccommodating holes 53, the piston 43 a being urged elastically in thedownward direction by means of these springs 46.

The engaging mechanism 41 comprises the aforementioned cylindricalsection 11 b, the six connecting holes 17, the six steel balls 18, andthe six retainers 19, and it is constituted in the following manner.Each of the steel balls 18 is held movably in the radial direction in aretainer 19 fitted inside a connecting hole 17. In clamping, each steelball 18 is pressed towards the outer side by the ring-shaped engagingsection 49 of the piston rod 43 b and is caused to engage with theengaging section 36 of the bush 31, whilst in releasing of the clamp,the steel ball 18 moves towards the inner side and becomes partiallyaccommodated in the recess section 50 of the piston rod 43 b.

As shown in FIG. 6, the first positioning mechanism 5 is provided on oneside of the clamping mechanism 4, and this first positioning mechanism 5comprises the first tapered pin 60 which is fixed to the base body 2,and the first tapered collet 34 which is provided on the pallet 3 insuch a manner that it can be fitted tightly over a full circumference oftapered shaft section 61 of the first tapered pin 60, from above.

The first tapered pin 60 comprises an integrally formed fullcircumference tapered shaft section 61 in the upper half portion thereofand a small diameter shaft section 62 in the lower half portion thereof.The outer circumferential face of the full circumference tapered shaftsection 61 is formed with a tapered face 61 a which reduces in diameterin the upward direction, and the lower end section of the fullcircumference tapered shaft section 61 is formed into a circular barshape. The lower end portion of the full circumference tapered shaftsection 61 fits into the accommodating hole 15 of the large diametersection 11 a, and the small diameter shaft section 62 thereof fitsinside the recessed hole 15 a, the small diameter shaft section 62 beingfixed to the reference body 11 by means of a bolt 63.

As shown in FIG. 6 to FIG. 8, the outer circumferential face of thefirst tapered collet 34 is formed with a circular cylindrical face andthe inner circumferential face of the tapered collet 34 is formed with atapered face which reduces in diameter in the upwards direction, in sucha manner that it is able to make close contact with the tapered face 61a of the full circumference tapered shaft section 61. An groove 34 athat is open at the upper end thereof, a groove 34 b that is open at thelower end thereof, and an elastically deforming section 34 c locatedbetween these two grooves, are formed respectively in four equidistantpositions about the circumference of the tapered collet 34, and thetapered collet 34 is able to deform elastically in a direction wherebyits diameter expands, by means of the elastic deformation of the fourelastically deforming sections 34 c. Incidentally, it is also possibleto form a groove 34 a with an open upper end, a groove 34 b with an openlower end, and an elastically deforming section 34 c, respectively, atthree equidistant positions about the circumference.

This tapered collet 34 fits inside the accommodating hole 31 a of thebush 31, slidably up and down, in a state of close contact with thesame, and a spring washer 64 for elastically urging the tapered collet34 in a downward direction is provided at the upper end of theaccommodating hole 31 a of the bush 31, between the same and the upperend of the tapered collet 34. The tapered collet 34 is engaged and heldat the lower end thereof by a holding ring 65, in such a manner that itdoes not become detached from the bush 31.

In positioning a pallet 3 with respect to the base body 2 in the firstpositioning mechanism 5, when the pallet 3 is pulled towards the basebody 2 by the clamping mechanism 4, then the inner circumferential faceof the first tapered collet 34 makes close contact with the tapered face61 a of the full circumference tapered shaft section 61, and the outercircumferential face of the tapered collet 34 makes close contact withthe inner circumferential face of the accommodating hole 31 a of thebush 31, whereby the pallet 3 is positioned to a high degree of accuracyin the horizontal direction with respect to the base body 2.

As shown in FIG. 6, the second positioning mechanism 6 is provided onthe opposite side to the first positioning mechanism 5 with respect tothe clamping mechanism 4, and this second positioning mechanism 6comprises the second tapered pin 66 which is fixed to the base body 2,and the second tapered collet 35 which is provided on the pallet 2 insuch a manner that it can be fitted over a two-faced tapered shaftsection 67 of the second tapered pin 66, from above.

The second tapered pin 66 comprises an integrally formed two-facetapered shaft section 67 in the upper half portion thereof and ashaft-shaped small diameter shaft section 68 in the lower half portionthereof. On the outer circumferential face of the two-face tapered shaftsection 67, there are formed respectively on the front side and rearside, two tapered faces 67 a which reduce in diameter in the upwarddirection, and respectively on the left-hand side and right-hand side,two vertical faces 67 b, the lower end portion of the two-face taperedshaft section 67 being formed into a circular bar shape. The lower endportion of the two-face tapered shaft section 67 fits is accommodated inthe accommodating hole 16 of the large diameter section 11 a, and thesmall diameter shaft section 68 thereof fits inside the recessed hole 16a, the small diameter shaft section 68 being fixed to the reference body11 by means of bolts 69.

The outer circumferential face of the second tapered collet 35 is formedwith a circular cylindrical face, and the inner circumferential face ofthe tapered collet 35 is formed with a tapered face which reduces indiameter in the upward direction, in such a manner that it can makeclose contact with the two tapered faces 67 a of the two-face taperedshaft section 67. The second tapered collet 35 has a similar structureto the first tapered collet 34. This tapered collet 35 fits inside theaccommodating hole 31 b of the bush 31, slidably up and down, and aspring washer 70 for elastically urging the tapered collet 35 in adownward direction is installed at the upper end of the accommodatinghole 31 b of the bush 31, between the same and the upper end of thetapered collet 35. The tapered collet 35 is engaged and held at thelower end thereof by a holding ring 71, in such a manner that it doesnot become detached from the bush 31.

In positioning a pallet 3 with respect to the base body 2 in the secondpositioning mechanism 6, when the pallet 3 is pulled to the base body 2by the clamping mechanism 4, then the front side portion and the rearside portion of the inner circumferential face of the second taperedcollet 35 make close contact with the two tapered faces 67 a situated onthe front side and rear side of the two-face tapered shaft section 67,the outer circumferential face of the tapered collet 35 makes closecontact with the inner circumferential face of the bush 31, and thepallet 3 becomes positioned in such a manner that it will not rotate ina forward or rearward direction about the first positioning mechanism 5,in other words, in such a manner that it will not rotate about avertical axis with respect to the base body 2.

Next, operation of the positioning and fixing device 1 for a pallet asdescribed above will be explained.

After setting of work piece on the pallet 3, as illustrated in FIG. 5and FIG. 6, the pallet 3 is transported onto the base body 2, the frontend portion of the cylindrical section 11 b is inserted into therecessed hole 30 b, the first tapered collet 34 is caused to coincidewith the full circumference tapered shaft section 61 and the secondtapered collet 35 is caused to coincide with the two-face tapered shaftsection 67.

Next, when hydraulic pressure is supplied to the clamping hydrauliccylinder 40 in a state where no hydraulic pressure is supplied to theclamping release oil chamber 45, and the piston 43 a is driven downwardsby the hydraulic pressure, then the piston rod 43 b also movesdownwards. Therefore, the plurality of steel balls 18 accommodatedpartially in the recessed section 50 are pushed out towards the outerside by the ring-shaped engaging section 49, and each of the steel balls18 engages with the engaging section 36 of the bush 31 and causes aclamping force to act on the bush 31, thereby causing the pallet 3 tobecome fixed to the base body 2.

In the first positioning mechanism 5, in a state where the clamping isreleased as in FIG. 6, the first tapered collet 34 is urged elasticallyin the downward direction by the spring washer 64, and this taperedcollet 34 is positioned at its lowest limit with respect to the bush 31.If the clamp is driven and the pallet 3 is lowered, the tapered collet34 is caused to slide upwards relatively with respect to the bush 31,whilst maintaining a state of close contact with the tapered face 61 aof the full circumference tapered shaft section 61, by means of elasticdeformation of the elastically deforming section 34 c. When the abuttingface 37 of the pallet 3 has abutted against the horizontal receivingface 14 of the base body 2, and the pallet 3 has become positioned in ahorizontal attitude, then the inner circumferential face of the taperedcollet 34 makes close contact with the tapered face 61 a of the fullcircumference tapered shaft section 61 and the outer circumferentialface of the tapered collet 34 makes close contact with the innercircumferential face of the accommodating hole 31 b of the bush 31,whereby the pallet 3 becomes positioned with a high degree of accuracyin the horizontal direction, with respect to the base body 2 (see FIG.9, FIG. 10).

In the second positioning mechanism 6, in a state where the clamping isreleased as in FIG. 6, the second tapered collet 35 is urged elasticallyin the downward direction by the spring washer 70, and is positioned atits lowest limit with respect to the bush 31. If the clamp is driven andthe pallet 3 is lowered, the tapered collet 35 is caused to slideupwards relatively with respect to the bush 31, whilst maintaining astate of close contact with the two tapered faces 67 a of the two-facetapered shaft section 67, by means of elastic deformation of theelastically deforming section.

In this case, there is a very slight gap between the tapered collet 35and the vertical faces 67 b of the two-face tapered shaft section 67.When the abutting face 37 of the pallet 3 has abutted against thehorizontal receiving face 14 of the base body 2, and the pallet 3 hasbecome positioned in a horizontal attitude, then the front side portionand the rear side portion of the inner circumferential face of thetapered collet 35 make close contact with the front and rear taperedfaces 67 a of the two-face tapered shaft section 67 and the outercircumferential face of the tapered collet 35 makes close contact withthe inner circumferential face of the accommodating hole 31 b of thebush 31, whereby the pallet 3 becomes restricted from rotating about avertical axis with respect to the base body 2 (see FIG. 9, FIG. 10).

As described above, since the pallet 3 is positioned to a high degree ofaccuracy in a horizontal position with respect to the base body 2, bymeans of the first positioning mechanism 5, and since it is positionedin such a manner that it may not rotate about the vertical axis withrespect to the base body 2, by means of the second positioning mechanism6, then the pallet 3 becomes positioned to a high degree of accuracy inthe horizontal direction, with respect to the base body 2. Moreover, theabutting face 37 of the pallet 3 abuts against the receiving face 14 ofthe base body 2, thereby causing the pallet 3 to be positioned to a highdegree of accuracy with respect to the base body 2, in the verticaldirection also.

In releasing the fixing of the pallet 3 from the state shown in FIG. 9and FIG. 10, when the hydraulic pressure in the clamping oil chamber 44is released and hydraulic pressure is supplied to the clamping releaseoil chamber 45, the hydraulic pressure acting on the lower face of thepiston 43 a causes the piston 43 a to be driven upwards against theelastic force of the springs 46, and hence the piston rod 43 b alsomoves upwards. Consequently, the ring-shaped engaging section 49 alsomoves upwards, the steel balls 18 which had been pressed towards theouter side by the ring-shaped engaging section 49 move towards the innerside, and the steel balls 18 become partially accommodated in the recesssection 50. Consequently, the engagement between the steel balls 18 andthe bush 31 is released, and the pallet 3 is separated from the basebody 2 and ejected in an upward direction.

According to the positioning and fixing device 1 for pallets describedabove, the following advantages are obtained.

Since the pallet 3 can be positioned in a horizontal attitude by meansof the abutting face 37 of the pallet 3 abutting against the receivingface 14 of the base body 2, the pallet 3 can be positioned to a highdegree of accuracy in the horizontal direction with respect to the basebody 2 by means of the first positioning mechanism 5, and the pallet 3can be positioned to a high degree of accuracy in such a manner that itdoes not rotate about a vertical axis with respect to the base body 2,by means of the second positioning mechanism 6, then it is possible toposition the pallet 3 with a high degree of accuracy in the horizontaldirection and vertical direction with respect to the base body 2, and itis possible to position the pallet with a high degree of accuracy insuch a manner that it does not rotate about a vertical axis.

Since the pallet 3 is positioned in the horizontal direction withrespect to the base body 2 by means of the two positioning mechanisms 5,6, and the pallet 3 can be pulled towards and fixed to the base body 2by means of a single set of clamping mechanism 4 provided in theapproximately central portion of the base body 2 and the pallet 3, thenit is possible to reduce the number of clamping mechanisms andpositioning mechanisms, each being constituted by a large number ofcomponents and having a complex structure, and it is possible tosimplify the structure of the pallet positioning and fixing device 1.

Since the first tapered collet 34 and the second tapered collet 35 areboth provided on the pallet 3, then even in cases where wearing orsettling has occurred in the tapered collets 34, 35, due to repeated useof the pallet 3, these effects are not received by the base body 2, andtherefore error does not occur in the position of the pallet whenanother pallet 3 is positioned and fixed thereon.

Since the receiving face 14 of the base body 2 is a ring-shaped face ofa predetermined width, being formed as a ring-shaped face whichintersects substantially with the positioning mechanisms 5, 6, then thepallet 3 can be caused to make close contact with the receiving face 14in a stable manner, and hence the pallet 3 can be positioned in thevertical direction.

Since spring washers 64, 70, which respectively impel the taperedcollets 34, 35 elastically downward, are provided on the bush 31, thenthe tapered collet 34 makes close contact with the tapered face 61 a ofthe full circumference tapered shaft section 61, and the tapered collet35 makes close contact with the two tapered faces 67 a of the two-facetapered shaft section 67, whereby it is possible to position the pallet3 to a high degree of accuracy in the horizontal direction, with respectto the base body 2.

Next, various modifications wherein the foregoing embodiment ispartially modified will be described.

1) As means for elastically urging the tapered collets 34, 35 downward,instead of a spring washer, it is possible to use any one of; anotherurging member, an elastic member made from rubber, an elastic membermade from synthetic resin, or a gas cylinder or hydraulic oil cylinder.

2) It is also possible to apply the present invention to a positioningand fixing device for a pallet as illustrated in FIG. 11. In FIG. 11,the same reference numerals are used for items which are similar tothose of the foregoing embodiment, and further description thereof isomitted.

The positioning and fixing device 1A is provided with a base body 2A, asingle set of clamp mechanism 4A which is capable of fixing a pallet 3Aby pulling the pallet 3A towards the base body 2A side at substantiallythe central portion of the pallet 3A, a first positioning mechanism 5for positioning the pallet 3A in the horizontal direction with respectto the base body 2A, and a second positioning mechanism 6 forpositioning the pallet 3A in such a manner that it does not turn about avertical axis with respect to the base body 2A. The reference body 11Aof the base body 2A comprises an upper reference body 80 and a lowerreference body 81, the upper reference body 80 being constituted by alower large diameter section 80 a and a tubular shaped section 80 bwhich extends upwards from the large diameter section 80 a, and thelower reference body 81 being constituted by a large diameter section 81a, a tubular section 81 b which extends upwards from the large diametersection 81 a and an engaging section 81 c which projects from the lowerend of the large diameter section 81 a, and the like. The tubularsection 81 b of the lower reference body 81 is inserted inside the largediameter section 80 a and the tubular section 80 b of the upperreference body 80. The reference body 11A is fitted to the base plate 10at the engaging section 81 c of the lower reference body 81, and in thisstate, it is fixed to the base plate 10 by means of bolts (notillustrated) which pass through the upper reference body 80 and thelower reference body 81.

A horizontal receiving face 14A for receiving and restricting the pallet3A is formed on the upper face of the large diameter section 80 a of theupper reference body 80, this receiving face 14A being a ring-shapedface of a predetermined width which is formed as a ring-shaped face thatintersects substantially with the first and second positioningmechanisms 5, 6. A ring-shaped guide member 82 which guides the movementof the steel balls 18 and constitutes a portion of an engaging mechanismdescribed hereinafter is fitted inside the tubular shaped section 80 b.A collar section 83 is formed towards the inner side on the upper endsection of the tubular shaped section 80 b, and the movement of theguide member 82 in the upward direction is restricted by the collarsection 83.

Two accommodating holes 15, 16 for accommodating a first tapered pin 60of a first positioning mechanism 5 and a second tapered pin 66 of asecond positioning mechanism 6 are provided in two symmetrical positionswith respect to an axis 84, in the upper face of the large diametersection 80 a, and recessed holes 15 a, 16 a which connect to the lowerend of the respective accommodating holes 15, 16 are also formedtherein.

A rod insertion hole 85 through which the piston rod 101 b of the clampmechanism 4A passes is formed inside the lower reference body 81, and adust seal 86 for preventing infiltration of cutting chips or dust isprovided on the inner circumferential face of the upper end portion ofthe rod insertion hole 85. A seal member 87 for performing sealing isprovided on the outer circumferential portion of the engaging section 81c.

The pallet 3A comprises a pallet main body 30 which is substantiallysquare in shape, and a bush 31A formed with an abutting face 37A whichabuts against the receiving face 14A of the base body 2A. The palletmain body 30 is similar to that of the aforementioned embodiment, andthe bush 31A is fitted into the accommodating hole 30 a formed on thelower portion of the pallet main body 30 and fixed by a bolt.

Two circular tube shaped accommodating holes 31 a, 31 b, into whichfirst and second tapered collets 34, 35 are installed symmetrically withrespect to the axis 84, are formed in the lower portion of the circulartube shaped bush 31A, these holes 31 a, 31 b being open at the lowerends thereof. A recessed hole 91 in which the tubular shaped section 80b of the upper reference body 80 is accommodated is formed having a openlower end, in the vicinity of the axis 84 of the bush 31A, and anengaging shaft section 92 which projects downwards is formed in thecentral portion of the recessed hole 91. A small diameter section 92 ahaving a reduced diameter in a neck shape is formed in the engagingshaft section 92, in an intermediate region in the upward and downwarddirection, and a tapered engaging section 92 b with which the steelballs 18 of the clamping mechanism 4A engage in the clamping action, isformed on the front end of the small diameter section 92 a. Furthermore,a horizontal, ring-shaped abutting face 37A which abuts against thereceiving face 14A of the large diameter section 80 a of the upperreference body 80 is provided on the lower face of the bush 31A.

The clamp mechanism 4A is provided in the central portion of the basebody 2A and the pallet 3A, and the clamp mechanism 4A comprises ahydraulic cylinder 40A for generating a clamping force and a clampingrelease force, and an engaging mechanism 41A for pulling the pallet 3Ato the base plate 10 side.

A double-acting hydraulic cylinder 40A is disposed inside the centralportion of the lower reference body 81, and the hydraulic cylinder 40Acomprises a cylinder hole 100 formed in the lower reference body 81, apiston member 101 for transmitting clamping force and clamping releaseforce, a clamping oil chamber 103 for generating clamping force and aclamping release oil chamber 104 for generating clamping release force.

The piston member 101 comprises an integrally formed ring-shaped piston101 a and cylindrical shaft shaped piston rod 101 b. The piston 101 a isfitted slidably up and down in the cylinder hole 100, and a sealingmember 105 is provided on the piston 101 a. The piston rod 101 b ispassed slidably up and down through the inside of the rod insertion hole85, and a sealing member 106 for sealing the clamping oil chamber 103 isalso provided. Six connecting holes 107 which connect through from theinner circumferential face to the outer circumferential face are formedin the vicinity of the top end portion of the piston rod 101B, and aring-shaped retainer 108 holding a steel ball 18 is engaged with andfixed into each of the respective connecting holes 107.

A cylindrical sleeve member 111 for preventing infiltration of cuttingchips, dust, or the like, is installed slidably in the upward anddownward direction inside the piston member 101, and a spring 112 forelastically urging the sleeve member 111 in an upward direction isdisposed inside the sleeve member 111, the lower end of the sleevemember 111 abutting against a spring receiving member 113 which receivesthe spring 112, and the spring receiving member 113 being screw fittedinto the piston 101 a. In a state where the pallet 3A is separated fromthe base body 2A, the sleeve member 111 is driven by the spring 112 tothe upper end of the piston rod 101 b, and cutting chips, dust, or thelike, are prevented from infiltrating into the interior of the pistonmember 101. In an unclamped state of clamped state of the pallet 2A, thelower end face of the engaging shaft section 92 abuts against the upperend face of the sleeve member 111, and under the weight of the pallet3A, the sleeve member 111 is pressed down against the action of thespring 112.

The engaging mechanism 41A is constituted by the aforementioned guidemember 82, the engaging shaft section 92 formed in the bush 31A, the sixconnecting holes 107 formed in the piston rod 101B, the six steel balls18, and the six retainers 108, and the like. A tapered face 82 a forguiding the movement of the steel balls 18 towards the axis 84 duringclamping is formed on the inner circumferential face of the upper halfportion of the guide member 82, and a ring-shaped engaging section 82 bwhich drives the steel balls 18 towards the axis 84 is formed on thelower end of the tapered face 82 a. Each of the steel balls 18 is heldmovably in the radial direction in a retainer 108 fitted set inside aconnecting hole 107. When the piston rod 101 b descends during clamping,in accordance with this, the steel balls 18 move towards the axis 84along the tapered face 82 a of the guide member 82, whereupon theyengage with the ring-shaped engaging section 82 b and are pressedtowards the axis 84, the steel balls 18 engage with the engaging section92 b of the engaging shaft section 92, and a clamping force istransmitted via the bush 31A to the pallet 3A.

The first positioning mechanism 5 and the second positioning mechanism 6are similar to those of the embodiment described above, and the firsttapered pin 60 and the second tapered pin 66 are accommodatedrespectively in the accommodating holes 15, 16 of the large diametersection 80 a, and are fixed to the reference body 11A by means of holts63, 69.

To describe the operation of this positioning and fixing device 1A, whenhydraulic pressure is supplied to the clamping oil chamber 103 in astate where no hydraulic pressure is supplied to the clamping releaseoil chamber 104, and the piston 101 a is driven downwards by thehydraulic pressure, then the piston rod 101 b also moves downwards.Therefore, the steel balls 18 installed movably in the rearwarddirection in the piston rod 101 b move towards the axis 84 along thetapered face 82 a of the guide member 82, whereupon they engage with thering-shaped engaging section 82 b, are pressed towards the axis 84, andthe steel balls 18 then engage with the taper shaped engaging section 92b formed in the engaging shaft section 92. Consequently, a clampingforce is transmitted to the pallet 3A via the steel balls 18 and thebush 31A, and the pallet 3A is pulled towards and fixed to the base body2A.

In this case, the abutting face 37A of the pallet 3A abuts against thereceiving face 14A of the base body 2A, thereby causing the pallet 3A tobe positioned to a high degree of accuracy with respect to the base body2A, in the vertical direction.

The positioning in the horizontal direction as achieved by means of thefirst positioning mechanism 5 and the second positioning mechanism 6 issimilar to the embodiment described above and explanation thereof isomitted here.

According to this positioning and fixing device 1A for the pallet,similarly to the embodiment described above, the pallet 3A can bepositioned in the vertical direction by means of the abutting face 37Aof the pallet abutting against the receiving face 14A of the base body2A, whilst the pallet can be positioned to a high degree of accuracy inthe horizontal direction by means of the first positioning mechanism 5and the second positioning mechanism 6. Moreover, since the tubularshaped section 80A of the upper reference body 80 accommodated in therecessed hole 91 of the bush 31A is relatively short in the clampedstate, then when changing the pallet 3A, it is possible to eject thepallet 3A from the base body 2A simply by raising it a short distance.

3) As shown in FIG. 12, in a base body 2B of a positioning and fixingdevice 1B for a pallet, in addition to providing a first positioningmechanism 5B for positioning a pallet in the horizontal direction withrespect to a clamping mechanism 4B, it is also possible to provide asecond positioning mechanism 6B for positioning the pallet in such amanner that it does not rotate about a vertical axis, on the other sideof the clamping mechanism 4B, and it is also possible to provide twopositioning mechanisms 120, 121 on either side of the clamping mechanism4B. The respective positioning mechanisms 5B, 6B, 120, 121 each have areceiving face provided on the base body 2B and an abutting faceprovided on the pallet, it is possible to position the pallet in thevertical direction by abutting the abutting faces against the receivingfaces, respectively. Even if the positioning mechanisms 120, 121 canonly carry out positioning in the vertical direction, it is alsopossible to adopt mechanisms such as the first and second positioningmechanisms 5B, 6B which are capable of carrying out positioning in thevertical direction and the horizontal direction.

4) The aforementioned embodiment and the modifications thereof weredescribed with respect to an example of a clamping mechanism of a typewhich performs clamping by means of steel balls, but the clampingmechanism is not limited to that described above, and variousconventional commonly known clamping mechanisms may be applied.

5) The aforementioned embodiment and the modifications thereof wereapplied to an example of a case where the base body is fixed to thetable of a machine tool, but they might also be applied to a base bodywhich is disposed in the form of an actual table.

1. A pallet positioning and fixing device for positioning and fixingreleasably a work piece holding pallet on a base body provided on atable or provided as the table itself of a machine tool, characterizedin that: a horizontal receiving face is formed on an upper face of saidbase body, and an abutting face capable of positioning said pallet in ahorizontal attitude by abutting against said receiving face is providedon a lower face of said pallet; a single set of clamping mechanismcapable of pulling said pallet towards said base body and fixing thesame thereto is provided substantially in the central portion of saidbase body and said pallet; and a first positioning mechanism forpositioning said pallet in a horizontal direction with respect to saidbase body is provided on one side of said clamping mechanism, and asecond positioning mechanism for positioning said pallet with respect tosaid base body so as to prevent said pallet from rotating about avertical axis is provided on the other side of said clamping mechanism.2. A pallet positioning and fixing device according to claim 1,characterized in that said first positioning mechanism comprises a fullcircumference tapered shaft section fixed to said base body and a firsttapered collet provided on said pallet in such a manner that said firsttapered collet can be fitted tightly over said full circumferencetapered shaft section from above.
 3. A pallet positioning and fixingdevice according to claim 2, characterized in that said secondpositioning mechanism comprises a two face tapered shaft section fixedto said base body and a second tapered collet provided on said pallet insuch a manner that said secondd tapered collet can be fitted over saidtwo face tapered shaft section from above.
 4. The pallet positioning andfixing device according to any one of claims 1 to 3, characterized inthat said receiving face is a ring shaped face of a predetermined widthand is formed as a ring shaped face which substantially intersects withsaid first and second positioning mechanisms.
 5. A pallet positioningand fixing device according to claim 3, characterized in that elasticmembers for respectively urging said first and second tapered colletselastically in a downward direction are provided.